The present invention relates to devices for releasably holding a movable body in a given position with respect to another body.
Thus, the device of the present invention may be used in machine tools which have bodies at least one of which is movable relative to the other, for the purpose of releasably holding such a movable body in a predetermined position with respect to the other body.
The present invention relates in particular to that type of device where a frame is formed by a pair of opposed end walls and a pair of opposed fixed walls which extend between and are fixed to the end walls, with a pair of opposed clamping walls extending across the space between the fixed walls and being spreadable apart from each other to a holding position pressing against bodies as referred to above for releasably holding at least one movable body at a given position with respect to the other body.
Such a device may include between the clamping walls a control plate which is shiftable between the end walls in clamping and non-clamping directions with two rows of tiltable spreading bodies situated on opposite sides of the control plate and engaging the latter as well as inner surfaces of the clamping walls. Suitable springs act on the spreading bodies to urge the latter to tilt in response to movement of the control plate in a clamping direction for spreading at least one of the clamping walls away from the other so that the device will assume its position pressing against the movable body to releasably hold the latter at a predetermined position.
A device of the above general type is disclosed, for example, in the German publication DAS 16 27 043. With this known holding device the clamping walls form a one-piece housing with the end walls and fixed walls which extend therebetween. The spreading of the clamping walls apart from each other to provide the required clamping action is brought about by deformation or bending of these clamping walls which form a unit with the remainder of the housing.
Another type of known clamping device of the above general type is disclosed in German patent 1,750,592. With this type of clamping device the opposed clamping walls are connected with the remainder of the housing either by being bolted or pinned thereto, so that in this case also the required clamping action which is achieved by spreading of the clamping walls apart from each other results from deformation or bending of these clamping walls.
Both of the above types of known clamping devices have the disadvantage of providing, on the one hand, only an extremely reduced clamping force as a result of the required deformation of the clamping walls and on the other hand of producing a non-uniform clamping force which varies along each clamping wall depending upon the extent to which the latter is curved with the clamping force being practically zero at the location where the clamping walls are connected to the remainder of the housing.
With the second of the above known devices where the clamping walls are connected with the remainder of the housing by being bolted or pinned thereto, there is a certain advantage in the ease with which the parts are assembled, but on the other hand there is the disadvantage that axial movement will provide at the clamping wall a jamming or shearing of the connecting bolt or pin. In the event that this latter disadvantage occurs, then the spreading elements will no longer return to their initial positions after a clamping operation, in readiness for the next clamping operation, and the entire device must be completely disassembled, with this latter operation in itself providing the possibility of breaking of individual spreading elements.
The first of the above-mentioned known types of clamping devices which are representative of the state of the art has the further disadvantage of rendering the assembly of the components and in particular the introduction of the spring-loaded spreading elements extremely difficult to carry out because of the one-piece construction of the unit which includes the clamping walls, while the second of the above devices which represent the state of the art has the disadvantage of requiring a relatively complex construction.